IALA-A and IALA-B Navigation Marks and Atons

Posted by Director of Education on March 28, 2017 under Bareboat Charter, Coastal Navigation, Crew, Rules of Right of Way, Skipper | Comments are off for this article


Getting confused about Lateral Navigation Marks and ATONs? There are two systems in the world. IALA-A and IALA-B. Basically, the colors are opposite but here is the infographic.

This information and everything else you need to know about coastal navigation is in the NauticEd Coastal Navigation Course. It’s only $39. Upon completion, the course is added to your globally accepted sailing resume.

Info graphic showing IALA-A and IALA-B systems

Infographic showing IALA-A and IALA-B systems

Here is a world map of where these systems are used.

  • On IALA-B use “red – right – returning”. i.e. put the red buoy on your right when returning.
  • On IALA-A you use the mnemonic “Is there any red port left” to memorize which color buoy you pass on which side of your boat (when returning). i.e. take red buoy to your port (which is the left side of your boat.). Universally, “Is there any red port left?” also works for memorizing what color lights are on your boat. i.e. The red light is mounted on your port side of your boat which is the left side of your boat. For IALA-A is is also easy to remember that you match the color of your boats light to the buoy light. i.e. Red to Red and Green to Green.
IALA Regions

IALA Regions

Just FYI: IALA stands for International Association of Marine Aids to Navigation and Lighthouse Authorities.

Lights on Navigation Markers (ATONS)

Posted by Director of Education on August 17, 2016 under Coastal Navigation, Crew, Rules of Right of Way, Skipper | Comments are off for this article

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This is a partial section out of our NauticEd Skipper Course and our NauticEd Coastal Navigation Course which discusses lights on ATONs. If you find this useful then perhaps you might consider taking either of the courses. Coastal Navigation is only $39 and covers most everything you need to know when navigating a yacht. When you pass the course it automatically adds to your NauticEd Sailing Resume.

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ATONs are Aids to Navigation. The term is primarily used in the United States and Canada. Most of the rest of the world refer to them as Navigation Marks.

Lights are installed on some ATONs. The lights are usually alternating on and off on some consistent interval to distinguish one ATON from another. The series of “ons” and “offs” are listed on the charts. This helps identify exactly which ATON you are observing. The time between each series is called a “period”.

Lighted ATONs are grouped into Flashing, Quick, Occulting and Isophase.


  • Flashing: A light in which the total duration of light in each period is clearly shorter than the total duration of darkness – and in which the flashes of light are all equal in duration.
    • Example: a quick flash on then a longer period off
    • Example: the flashes might be grouped meaning that the ATON flashes quickly a number of times followed by a longer period of dark then repeating.
  • Quick Light: A light turning on more than 60 (but less than 80 flashes) per minute.
  • Occulting: Showing longer periods of light than darkness (opposite of flashing)
  • Isophase: showing equal periods of light and darkness – remember that “iso” means same.
  • A Long Flash: (L Fl.) A light which exhibits a long flash of 2 seconds followed by a period of longer darkness.
  • Morse Code: (Mo. (letter)) A Morse coded letter

Colors of lights are listed with the ATON. They are red (R), green (G), yellow (Y), and white (W). Blue is reserved for law enforcement. Or if the color is not listed then it is white.

Examples of the various types are shown below:

ATON Lights Green

ATON Red Lights

There can also be a composite group flashing light. In the example below the green light flashes twice then one – then repeats after some time.


You can identify the lights on the charts from the information next to the light. In the example below, the Bifurcated Lateral Maker “U” flashes composite green twice then once every 6 seconds – Fl G (2+1) 6s, while the Green Lateral Can number “9” flashes green twice every 6 seconds – Fl G (2) 6s.


At night, you’ll be able to pick out the lights against their backdrop of city lights because of their alternating nature. In the example below you can see Fl G (2+1) 6s and Fl R (4) 6s. Notice however, that you have to concentrate on one at a time, so that the other does not distract you.

Flashing Lights example

Here is a slightly visually annoying summary.

Fl R Fl R (2) 5s QF Occ Fl R Iso Fl R Composite Fl (2+1) 6s
flashing light Light Flashing 2 5s Quick Flashing Light Occulting Flashing Light Iso Flashing Light Composite Flashing Light



Caution Lights
In most countries, including the USA, the white quick flashing light is used to mark Cautionary ATONS

Safe Water Marks
In many countries, including the USA, the Safe Water mark is used and is a white flashing Morse code “A”. One short followed by one long and then repeating at least 8 times per minute. Just remember A – ok.

But also, a safe water mark can be exhibited by other white lights as shown specifically on the chart.

A long 2 second flash over a 10 second period (L Fl. 10s) is also reserved for a safe water mark.

Safe Water Light

Special Purpose Marks
If a Special Purpose Buoy is lighted it displays a yellow light with fixed or slow flashing characteristics.

Isolated Danger Marks
If lighted, a white light shall be used and the chart will announce the flashing sequence. The image below shows Fl (2) 5s but this is just an example. Any time you see a white flashing light you should be on guard.
Animated Isolated Danger Mark

Sector Lights
Sector lights are sectors of color that are placed on lantern covers of certain lighthouses to indicate danger bearings. On a chart, the sector bearings are true bearings according to the chart and must be converted from magnetic bearing if using a compass. A red sector indicates a vessel is potentially in danger of running aground. Note however, that red can be seen beyond the danger zone as well.

Sector light animated

This is also seen here below in a real case of a Nautical Chart #12354 Long Island Sound Eastern Port. Can you spot the Red Sector light?

Spot the Red Sector Light

Spot the Red Sector Light

Cardinal Mark Lights

Cardinal Marks if lighted use white quick flash lights. They are easily remembered from thinking of a clock dial.

  • North – Continuous quick flash
  • East – 3 quick flashes (3 o’clock)
  • South – 6 quick flashes followed by a long flash (6 o’clock)
  • West – 9 quick flashes (9 o’clock)



Light Lists
Publications that list all the lights usually exist for each country. In the United States the Coast Guard publishes the Light List, which can be found at http://www.navcen.uscg.gov/?pageName=lightlists For your country, or the country you are visiting, just search on “coast guard light list (country)” or you might replace coast guard with navigation or atons.

Below is an excerpt. Each ATON is listed by number (from the index at the back of the light list), it’s name and any distinguishing location, its lat and long position, its characteristic, height (if it is a light house), the range that the light can be seen from, the type of structure and any remarks about the light.

Light List Excerpt

Light List Excerpt

Putting It All Together
The graphic animation below shows what a harbor entrance may look like at night.


And the corresponding chart symbols might look like this below

Lights on a Chart

Lights on a Chart

Take the NauticEd Skipper Course and our NauticEd Coastal Navigation Course. These courses are packed with information you should know as a responsible sailor.

skipper course

Coastal Navigation Course

Sailing in Sydney Harbour

Posted by Grant Headifen on May 15, 2009 under Bareboat Charter, Coastal Navigation, Rules of Right of Way, Skipper | Be the First to Comment

[Not a spelling mistake – Harbor in Australia, New Zealand, England etc is spelled Harbour, along with colour, neighbour etc]

Sailing in Sydney Harbour

Sailing in Sydney Harbour

Thanks go out to Matt Hayes with Sydney by Sail who provided a sailboat for my wife, 8 month old daughter and myself to have a grand sailing tour of the Sydney harbor this past week. Sydney by sail is a very successful charter fleet out of Darling harbour in downtown Sydney. Their specialty is corporate day charters and corporate regatta races, but they also charter out to individuals wanting to soak up the sites of Sydney from the water.

I think she's about got the hang of it

I think she

The experience of sailing on the Sydney Harbour is not to be missed by anyone. Sailing under the Sydney harbor bridge and then right past the Sydney Opera house is one of those events that everyone should do at least once in their lifetime. The Opera house deserves every bit of awe that has been bestowed upon it and throughout the harbour the familiar sight of the shell design of the opera house can be seen.

The grand Sydney Opera House. View from the water.

The grand Sydney Opera House. View from the water.

What we also where able to obtain on this 8-12 knot breeze and cloudless day was an extensive photo shoot of the ATONS (Aids to Navigation) used by the IALA-A system.

The International Association of Lighthouse Authorities– A system is used in all parts of the world except the American Continent and Japan who use the IALA-B system. Under the IALA-B system most are familiar with the phrase RED – RIGHT- RETURNING.

Well RED- RIGHT – RETURNING doesn’t apply in the IALA-A system. As one leaves Darling Harbour and begins to follow the channel out towards the sea Red ATONS are kept on the right and Green on the left. (Opposite of IALA-B). It’s not confusing, it’s just opposite, right? Or is it left?

Green on the left when going out of the harbour

Green on the left when going out of the harbour

We also photographed some stunning lighthouse ATONS seen here below. And we even saw two cardinal marks – one telling us to stay south of it and the other to stay west.

A south Cardinal mark. Stay south for safe water.

A south Cardinal mark. Stay south for safe water.

On top of all that was an excellent opportunity to photo the rich and perhaps famous homes right on the waters edge in the harbour.

The Sydney harbour side houses. Lovely!

The Sydney harbour side houses. Lovely!

These homes where magnificent. Many were obviously built in the 60’s and 70’s and most have been recently renovated. These homes command a stunning view of the happenings in the harbour.

Home views of Sydney Harbour. Want one?

Home views of Sydney Harbour. Want one?

Sydney harbour is a very busy harbour with ferry boats constantly crossing our paths. Cruise ships often visit and there is literally thousands of sailboats moored up in coves all over.

On a busy Friday afternnon, (as I experienced on my last sailing visit to Sydney a few years ago) you literally have to dodge other sailboats every couple of hundred feet. A friend once racing in the Harbour had 3 collisions on he same day. Here is a pic of even a seaplane taking off in the harbour. Do you remember who has right of way over a seaplane?

So you’ve got to have your wits about you and you’d better be versed up on lights and rules of right of way. See the FREE NauticEd rules of right of way clinic.

Thanks again Matt Hayes and Sydney by Sail for an excellent sailing experience on the Sydney Harbour.

Matt Hayes, Sydney by Sail and Grant Headifen, NauticEd

Matt Hayes, Sydney by Sail and Grant Headifen, NauticEd

Coastal Navigation Clinic Launched

Posted by Grant Headifen on April 15, 2009 under Coastal Navigation | Be the First to Comment

Yesterday we launched our most requested clinic. Coastal Navigation! We’re very excited to have this course completed and up. It was written by our resident faculty member Captain Ed Mapes with Offshore Voyages. Ed has taught navigation courses with thousands of students on board his ocean learning passages.

The Coastal Sailing Navigation course incorporates most all the elements required by the United States Coast Guard Captain’s License Navigation section. Some of the topics covered are Coastal Sailing Navigation tricks and techniques using lines of position, gps, running fix, bearing fixes, true versus magnetic bearings, using navigation tools, calculate set and drift from tides and current, determine your heading with a known set and drift etc. In addition there is a review of the ATONs (aids to navigation) during the day and at night which was presented in the NauticEd skipper course.

The course is presented with lots of graphics and video’s explaining the navigation techniques from very basic terms to ensure everyone grasps the navigational concepts.

Watch a NauticEd Coastal Naviation video

If you’re taking your boat out beyond the harbor, then you’ll enjoy the NauticEd Coastal Navigation course.

A few rules and signs and lights to learn when sailing

Posted by Grant Headifen on January 25, 2009 under Rules of Right of Way, Skipper | Be the First to Comment

Once you’ve decided that you like it and you now want to learn to sail for yourself, there are just a few things to learn, actually quite a lot but don’t be intimidated – we all started sailing some where – some time.

The rules of right of way can be a bit daunting so that’s why we created the FREE rules of right of way clinic for all. Below however, is a graphic that anyone can use for learning the ATONS (aids to navigation). But the point to be careful of is that for the America’s it’s backwards from the rest of the world or is the rest of the world backwards? I Guess it’s 250 million against the rest right? Actually a few more vote on the American side. Here’s the map.

IALA-B and IALA-A system for ATONS

IALA-B and IALA-A system for ATONS

The IALA-B system is used by North-Central and South America and Japan and Philippines. The rest of the world uses the IALA-A system.

IALA stands for the International Association of Marine Aids to Navigation and Lighthouse Authorities. There are just two systems IALA-A and IALA-B which operate in different parts of the world.This should be of particular note to those going chartering in various parts of the world. The essential difference is that the colors (colours) are swapped for entrances into harbors. The reason is said to be that the Americans during the war for independence wanted to confuse the British ships and so swapped the colors.

But you absolutely must learn these when learning to sail. But don’t worry they are easy. All you have to do is remember this “Red, Right, Returning” under the IALA-B system (North-central and South America and Japan and Philippines). That’s it! IE when you are returning from sea into the channel (or going upstream) keep the red markers on your right. In the case of the preferred channel take notice of what ever color is on top, that is, if red is on top then keep the marker on your right for the preferred channel. Red Right Returning! Right?

Confused? Well count yourself lucky living in today’s times – there used to be some 30+ systems until the IALA group was formed.

IALA-B and IALA-A system

IALA-B and IALA-A system

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